This function generates and returns all subsets of a list using recursion

subsets_recursive.java

    private static int numberOfElements;
    private static List<List<Integer>> subsets;
    private static List<Integer> currentSubset, elements;

    private static List<List<Integer>> subsetRecursive(List<Integer> elementsArg) {
        elements = elementsArg;
        numberOfElements = elements.size();
        subsets = new ArrayList<>();
        currentSubset = new ArrayList<>();

        System.out.println("Subsets of " + elements);

        subset(0);

        return subsets;
    }

    private static void subset(int index) {

        if (index == numberOfElements) {

            System.out.println(String.format("%s: %s", convertToZeroPaddedBinaryString(subsets.size(), numberOfElements), currentSubset));

            subsets.add(new ArrayList<>(currentSubset)); // clone original subset

        } else {
            subset(index+1);
            currentSubset.add(elements.get(index));

            subset(index+1);
            currentSubset.remove(currentSubset.size()-1); // pop last element from the subset
        }
    }

    private static String convertToZeroPaddedBinaryString(int number, int padWidth) {
        return String.format("%" + padWidth + "s", Integer.toBinaryString(number)).replaceAll(" ", "0");
    }